The aim of Project 3 is to investigate the role of metalloproteases in the development and progression of mouse epithelial cancers and to test the effects of anti-protease therapy in inhibiting these processes. By crossing transgenic models of cancer progression for the development and progression of mouse tumors into backgrounds that are null for specific proteases or protease inhibitors, or that over express specific protease inhibitors, it will be possible to determine when specific proteases or classes of proteases act, and which processes (growth, inflammation, invasion, metastasis, genomic instability) are downstream from protease action. In this funding cycle, the major focus of this project is to elucidate the contributions of individual active matrix metalloproteinases (MMPs) to neoplastic progression. We will concentrate on the human papilloma virus 16 early region targeted to the basal cells of the epidermis with the keratin 14 promoter, and, with Project 1, SV40 T-antigen targeted to prostatic epithelium with cryptidin-2 promoters. With CORE C, these will be crossed with mice on the same inbred background that are null or transgenic for specific metalloproteases or TIMPs, including MMP-2, MMP-3, MMP-9, MMP-13 and TIMP-1, alone and in specific double null combinations, and the impact on all aspects of progression from proliferation and apoptosis to influx of inflammatory cells, stromal activation, angiogenesis, matrix remodeling, malignant conversion, malignant grade and metastasis evaluated. In parallel, efficacy profiling of MMP inhibitor therapies will be done with Project 2. With CORES B and D expression patterns of the proteases and distribution of active proteases will be determined during progression in wild type mice, and then the impact of removing one MMP on the expression of other MMPs assessed. A major effort will be to seek the substrates that mediate these effects. The relative contributions of proteases from epithelial, inflammatory and/or stromal sources will be evaluated by transplanting neoplastic tissue or cells from one type of protease background onto animals of a distinct background. Angiogenesis, stromal activation and tumor development will then be assessed. Inactivating individual MMPs will likely have different effects than inhibiting the whole class of MMPs. Taken together, these model systems will elucidate the role of metalloproteases in the development of the premalignant lesions as well as in malignant conversion and metastasis, and provide proof-of-concept for anti-protease therapy in different stages of the development and progression of epithelial cancers.